I would also try replacing with a shackle and agree with Yngmar about tying off the boom.
We have a line with a small shackle that hooks onto the boom and a loop and a clip that goes round the grab rail. We then pull the taveller across and this stops the boom swinging.
We only take it off when using the main.
Be aware that the grab rail is not all that strongly attached to the cabin top, I used to do the same as you until one day arriving at the boat where I found the port side grab rail was (fortunately), still attached to the rope from the boom, but no longer attached to the cabin top. I plugged the holes that the screws had left with GRP filler and gel coat and re-attached the rail in a slightly different position such that the screws were secured into previously undamaged GRP. The slight difference in position is not noticeable unless you look very closely.
As for preventing the boom from swinging, I now use the midship mooring cleats to secure the rope ends, and have had no further problems.
Also Yngmar is right about the gooseneck lasting longer, I bought the boat when it was eight years old and the gooseneck for the boom was replaced within the first month of ownership. The new gooseneck is now nine years old and is in excellent condition, and the only differences that I am aware of is that I usually tie the boom off, and that the boat has been kept on a swinging mooring for the last seven years where there are no tidal or other currents in the harbour as such, and in consequence the boat always lays head to wind so the boom gets less of a battering from the weather.